A prior U.S. Pat. No. 3,226,137, filed on Apr. 16, 1962 and issued on Dec. 28, 1965 to applicant of this invention, relates to a means for securing a hose to a sleeve in a coupling device so that when the hose is charged, i.e., having water under pressure flowing through it, the force of the water assists in urging the hose in closer contact with the sleeve and coupling so as to increase the gripping action of the hose to the coupling unit.
The coupling described in U.S. Pat. No. 3,226,137 is particularly suitable for use with fire hoses whose individual lengths between couplings would be of the order of 500 feet or less and such hoses are charged with varying water pressures of zero to Hose Burst Pressure in lbs. per square inch. When the coupling is employed to couple hoses used for irrigation of large farms or similarly large land regions, difficulties arise because larger hose lengths are used, i.e., approximately 660 feet in length, and lower water pressures are used to charge the hoses, namely, approximately 50 lbs. per square inch. When pulling such large hoses, loaded with water under reduced pressures, one has to use a small gripping area between sleeve hose and coupling in order to achieve a high force per unit area of gripping. Such high force per unit area tends to tear into the hose portion being gripped so as to eventually render the hose incapable of being gripped because its body becomes damaged or shredded by such high forces per unit area. If one tries to enlarge the gripping area about the hose while under reduced water pressure so as to avoid such shredding of the hose, it is found that the lowered water pressure used for irrigating hoses is insufficient to affect gripping action so that there is leakage at the coupling, or the hose tends to slip out of its coupling.
I have discovered that by putting a taper, either single or double, either on the sleeve or on the wedge used in the coupler of U.S. Pat. No. 3,226,137, with the outside diameter of the mid-point of the taper being greater than the outside diameter of the ends of the taper, I increase the life of the hose in the following manner. The larger outside diameter of the sleeve serves as a ridge or line contact between sleeve and hose jacket, permitting the sleeve to be charged and sealed hydrostatically at the water pressure in the hose. When the hose is mechanically dragged across terrain, a very high pull of approximately 16,000 lbs. is developed. Such pull would normally cause this ridge of pressure to tear the hose at the region of gripping. But because of the taper in the sleeve or wedge, the sleeve area or contact area against the hose jacket increases, maintaining sufficient force per area between sleeve and hose jacket but not so much as to cause the sleeve to cut into the hose jacket.
In effect, the use of a tapered sleeve allows (a) a good gripping action between sleeve and hose jacket at low pressures if approximately 50 lbs. per square inch is provided over a narrow area of contact but (b) at greater water pressures or at very high end pulls of the hose, the gripping action is automatically distributed over a larger area so as to maintain proper gripping action. In effect, the change in geometry of the sleeve or wedge allows for the hose to accommodate pressure changes and increased end pull forces without jeopardizing the life of the hose.
Consequently, it is a principal object of this invention to be able to vary the end pulls on a long hose without damaging that portion of the hose being gripped in a coupling attached to such hose; this is accomplished by having the hose's pressure points with respect to a surrounding gripping sleeve in the coupling automatically change with changing end pulls and water pressures.